1. Field of the Invention
The present invention relates to a spin transistor, an integrated circuit, and a magnetic memory.
2. Description of the Related Art
Recently, new devices in which behaviors of a charge and a spin of an electron are simultaneously utilized, are being increasingly developed. Among others, in a spin transistor, ferromagnetic materials are used as a source electrode and a drain electrode, and an output characteristic is controlled by changing relative magnetization directions of the source electrode and drain electrode (for example, see S. Sugahara and M. Tanaka, Appl. Phys. Lett. 84 (2004) 2307, G. H. Fecher and C. Felser, J. Phys. D40, 1582 (2007), B. Balke et. al., Phys. Rev. B74 104405 (2006), and J. Phys.: Cond. Matt. 16, 3089 (2004)).
In the spin transistor, for example, a drain current (IDP) is increased when the relative magnetization directions of the source electrode and drain electrode are substantially parallel to each other, and a drain current (IDAP) is decreased when the relative magnetization directions are substantially anti-parallel to each other.
Preferably, an IDP/IDAP ratio, that is, a change in drain current between the parallelism and anti-parallelism of the relative magnetization direction is increased when the spin transistor is used in a magnetic memory or a reconfigurable logic circuit.
In order to increase the IDP/IDAP ratio, it is necessary to increase a spin polarization ratio of the magnetic materials used in the source electrode and drain electrode. However, even if the magnetic material having the spin polarization ratio of 100% can be used, unfortunately the IDP/IDAP ratio is deteriorated when a finite bias voltage is applied between the source electrode and drain electrodes.